Transcriptomic and Metabolomic Insights into Tissue- and Cultivar-Dependent Polysaccharide Accumulation in...

Polysaccharides are major bioactive constituents and quality-related components of Anoectochilus roxburghii. However, how polysaccharide accumulation varies among cultivars and tissues remains poorly understood. Here, crude polysaccharide content was quantified in leaves and stems of three cultivars, Yuanye (YY), Hongxia (HX), and Jianye (JY), and the underlying molecular basis was investigated using transcriptomics, targeted sugar metabolomics, and integrated transcriptome-metabolome analysis. Stems accumulated significantly higher levels of crude polysaccharides than leaves, whereas cultivar-dependent differences were most pronounced in stems. JY stems showed the highest crude polysaccharide content, reaching 357.81 mg g^-1 dry weight. Transcriptomic and metabolomic profiles clearly differentiated the cultivars and tissues. Metabolic differences were concentrated at a limited number of sugar-metabolic nodes, whereas the transcriptome showed extensive transcriptional reprogramming. Integrative analyses consistently implicated starch and sucrose metabolism, precursor-sugar interconversion, nucleotide-sugar biosynthesis, and sugar transport, partitioning, and intracellular allocation in differential polysaccharide accumulation. Glucose and D-fructose emerged as key hub metabolites linking transcriptional variation to sugar-metabolic remodeling. These results suggest that tissue- and cultivar-dependent polysaccharide accumulation is associated with coordinated changes in sucrose turnover, precursor sugar supply, nucleotide-sugar formation, and sugar partitioning, particularly in stems. This study provides molecular evidence for the selection of high-polysaccharide germplasm and quality evaluation of A. roxburghii.